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Cars travel on the rebuilt Vermont Route 107 in Bethel, Vt., earlier this month. Driving in America has stalled, leading researchers to ask: Is the national love affair with the automobile over?

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Fewer people at work, fewer people driving. It's a simple equation and one that a lot of experts pointed to as explanation for the notable drop in the total miles U.S. motorists clocked during the depths of the recession.

So, how to explain the fact that even as the economy finally is showing real signs of recovery the number of miles driven continues to decline. That report from the Federal Highway Administration is just the latest indication that Americans may be falling out of love with their automobiles.

In its report released this week, the agency said the number of vehicle miles traveled—VMT in the lingo of the transportation world—continued dropping during the first half of 2013. If the past were prologue, the numbers would have rebounded at least slightly to reflect the national rise in employment and income. (More from The Detroit Bureau: First Drive: 2014 Toyota Corolla)

In a study earlier this month, researchers from the John A. Volpe National Transportation Systems Center found that the number of miles individuals are driving has been declining sharply in recent years. That figure peaked at an average 900 miles per month in July 2004. By July 2012, it was down to 820 a month, a figure the researchers hadn't seen since the final years of the last millennium.

"For almost 40 years, auto usage, as measured by vehicle miles traveled, closely tracked real gross domestic product. VMT dropped during the most recent recession, as it has during previous ones. But unlike after prior recessions, it still hasn't recovered," Volpe researchers Don Pickrell and David Pace said in the report. (Read more: Honda Odyssey sets new safety standard)

"Some causes aren't new," said Pace. "Car ownership is essentially at its saturation point. Baby boomers drive less as they age. It's more expensive to purchase and own a car."

In addition, younger motorists may be driving less not only because of the cost of buying and operating a vehicle but also because of new restrictions on teen licensing. And there is evidence—some analytical, some anecdotal—that younger Americans are as likely to socialize by texting as by driving to meet in person with friends.(More from The Detroit Bureau: Nissan plans huge boost in US production, exports)

But the Volpe study discovered some other, unexpected shifts. There's been a notable drop in the vehicle miles traveled by young adults, a group that traditionally clocked more miles than most other groups, especially in a positive economic cycle.

The decline in driving has been much more significant among men than women.

Driving by men has, in fact, declined in every age group except those over 65.

The miles driven by women ages 20 to 34 have dropped since the early part of the new millennium.

Women older than their mid-30s are driving more, however, as are seniors of both genders.

Contrary to conventional wisdom, the two researchers contend the decline in vehicle miles traveled does not reflect a switch to other modes of transportation, whether mass transit, biking or even walking. And while there are clearly more telecommuters, the study found that that accounted for barely 1 percent of the overall decline. Even the growth in e-shopping didn't explain what is happening. (Read more: Ford recruits more to meet Fusion demand)

Other recent studies, including one produced by the University of Michigan Transportation Research Institute, have found similar signs that Americans are spending less time in their cars, waiting longer to get their driver's licenses and, in general, seeming to be falling out of love with the automobile.

"A growing number of Americans [feel] they [don't] need or want a personal car," contends researcher Art Spinella of CNW Marketing, whose study of carless households found the number has doubled over the past two decades and is on trend to reach as much as 10 percent this year.

Automotive proponents are buoyed by the fact that the U.S. new car market is growing at a double-digit pace this year. Consulting firm LMC Automotive now forecasts total sales will reach 15.6 million for all of 2013, up from 14.5 million the year before. That would, however, still be almost 2 million below the industry's prior, post-recession peak. And it remains to be seen how much more staying power the rebound has.

If anything, a study released by R.L. Polk this past month found that the age of the average vehicle on the road climbed from 11.2 years in 2012 to 11.4 years—even with the automotive market rebounding so fast that manufacturers are struggling to overcome capacity shortages. That's a record—and a big jump from the average 9.7 years Polk reported a decade ago. (More from The Detroit Bureau: From rock star to automotive entrepreneur)

"The car as a fetish of masculinity is probably over for certain age groups," transportation behavior analyst Nancy McGuckin told The Associated Press. "I don't think young men care as much about the car they drive as they use to."

Does it matter? The impact of a culture less enamored of the automobile could have a widespread impact, and not on just those who once wrote songs like "My Hot Rod Lincoln," or "Little Red Corvette."

Money once spent on automobiles appears to be diverting elsewhere, including the telecom industry, where smartphones have become for many the status symbol once defined by the car.

Since automobile manufacturing, sales and service are major sources of employment and a big factor in the nation's GDP, the shift could have tremendous repercussions for the future. The Volpe study even points to the already under-funded federal Highway Trust Fund, which could be even harder-pressed to cover the cost of infrastructure maintenance.

Every mile motorists cut out of their driving plans could have a significant impact on the future.